Electronic commerce, or e-commerce, generally refers to business conducted over an electronic medium such as the Internet (e.g., through the World Wide Web, or Web). Electronic commerce transactions typically are facilitated through applications such as web services, electronic shopping carts, file transfer protocol (FTP), secure FTP, electronic data interchange (EDI), email, and Universal Description, Discovery, and Integration (UDDI), among others. Electronic commerce transactions commonly are differentiated based on the type of trading partners that are interacting. For example, commerce between a business and a consumer generally is referred to as business-to-consumer (B2C) commerce, whereas commerce between businesses generally is referred to as business-to-business (B2B) commerce. Integration servers can be utilized to couple business and/or consumer trading partners and coordinate communication therebetween. By way of example, two businesses that employ disparate operating systems and/or applications can utilize an integration server to interact across internal and external networked computer systems.
In many instances, e-commerce can leverage information obtained from control systems and/or affect control systems. For example, a consumer purchasing an automobile through a dealer's web site may desire to know the lead time associated with building an automobile with a customized set of options. The dealer may query its manufacturing plants to ascertain whether an automobile with those options has been built or is going to be built. The result along with additional information can facilitate determining when such automobile will arrive at the distributor. If the purchaser decides to place a custom order (e.g., where there is no plan to build a car with the desired combination of options), the custom specification can be provided to the manufacturing plant and utilized to automatically configure one or more control systems therein. For example, the customer may have specified the color green as the external color of the automobile. This data can be conveyed to a control system and utilized to automatically select a suitable paint gun (e.g., a paint gun associated with green paint) and/or green paint when the automobile is being assembled.
Control systems commonly employ one or more industrial controllers. A typical industrial controller is a special purpose processing device for controlling (e.g., via an automated and a semi-automated means) industrial processes, machines, manufacturing equipment, plants, and the like. Such controllers can execute a control program or routine in order to measure one or more process variables or inputs representative of a status of a controlled process and/or effectuate outputs associated with control of the process. For example, an output module can interface directly with a controlled process by providing an output from memory to an actuator such as a motor, drive, valve, solenoid, and the like. In distributed control systems, controller hardware configuration can be facilitated by separating the industrial controller into a number of control elements, each of which can perform a different function. Particular control modules needed for the control task can be connected together on a common backplane within a rack and/or through a network or other communications medium. Various control modules can also be spatially distributed along a common communication link in several locations. Data can be communicated with these remote modules over a common communication link, or network, wherein any or all modules on the network communicate via a common and/or an industrial communications protocol.
Controllers within a control system can communicate with each other, with controllers residing in other control systems and/or with systems and/or applications outside of a control environment (e.g., business related systems and applications). Conventionally, such communication is achieved through a retry approach, wherein a controller can transmit a message (e.g., a request, information . . . ) to another entity, and if the message is not accepted by the entity (e.g., the entity/recipient is busy, inoperable, unavailable, unresponsive . . . ), the message transmission is aborted and the message is re-sent at a later time, or discarded. In another conventional approach, a message queue and an indexing scheme is utilized, wherein messages are stored in an array and an array index determines which message is transmitted. With this approach, even if a message transmission fails, the index is incremented and an attempt is made to send a next message. Eventually, failed transmissions are either re-sent or discarded.
Thus, conventional techniques usually require synchronous-based messaging, wherein the sender and the recipient are available to engage in a message exchange session. This can lead to, among other things, failed communications (e.g., messages that are not received or acted upon), delayed responses (e.g., as a function of the time difference between a sent message and a re-send), and additional overhead (e.g., consumption of processing cycles to review stored notifications, schedule re-transmissions and re-send messages). Moreover, industrial automation PLC programs that include messaging rely on users creating and maintaining library of ladder logic to implement message retry logic, communication protocols in ladder code, and other inconveniences.